The present invention is directed generally to systems and methods for door assemblies for railway cars, and, more particularly, to systems and methods for providing door assemblies for passenger rail vehicles having a door and a platform cooperatively arranged to operate with both high and low platforms.
For many years, the rail industry has been attempting to develop a reliable, safe, and cost effective passenger ingress and egress facility for use on rail passenger vehicles for use with platforms of different levels.
Various attempts have been made to solve this problem with little success. For example, U.S. Pat. Nos. 2,056,255; 2,220,035; and 2,415,341 each show examples of designs where the steps retract into the body of the train at high platforms and extend from the body of the train at low platforms. The steps are retractable and stow away in a compartment located under the train. A trap door, or stairwell platform, is closed at high platforms when the steps are in the stowed position. At low platforms, the operator-moves a manual lever to position the steps in an extended position and the stairwell platform is manually latched in an upper position. At high platforms, the steps are stowed via a manual actuating arm into a retracted position. The stairwell platform is manually closed into a lower position.
However, these designs are problematic in that the moveable steps are expensive, the extended position of the steps are not as stable and provide a undesirable feeling of instability, and the stowed position takes up substantial room in the undercarriage of the rail vehicle.
Another example is shown, for example, in U.S. Pat. No. 5,070,794, the entire disclosure of which is incorporated herein by reference for all purposes, which describes a sectioned door assembly. A sectioned door assembly employing a rail car door is divided into an upper sliding door and a lower sliding door, separate from the upper sliding door. The lower sliding door includes an integral mechanically operated latch and a high platform threshold. A stairwell platform is utilized to actuate the mechanically operated latch when the stairwell platform is slammed closed onto the high platform threshold. When impacted by the stairwell platform, the latch functions to automatically unlatch the upper door from the lower door, latch the lower door in place, and latch the stairwell platform onto the lower door. The high platform threshold supports the stairwell platform. The upper door assembly is typically supported at the top by a sliding connection to the door overhead structure. The top of the lower door panel is slidingly connected to the bottom of the upper door panel. The lower door panel is also connected via a slide assembly to the rail car body in the region of the high platform threshold. In addition, the bottom of the lower door panel is guided in a lower threshold.
This arrangement is disadvantageous for a number of reasons including: 1) it uses an excessive number of sliding elements which are susceptible to binding when the rail car racks and twists, 2) the lower door panel is not firmly restrained by its slide connection to the rail car structure and, therefore, tends to snag and become misaligned as it slides, and 3) it requires approximately six adjustment locations which must be set and maintained properly in order for the door to function properly, and 4) the two piece sliding door provides an additional ledge where accumulated ice and snow can cause the door to malfunction.
U.S. Pat. No. 3,724,396 shows another example of a sectioned door assembly having a stairwell platform with an interlocking latch assembly covering a fixed stair well. In this embodiment, the lower door section retracts under the rail vehicle car body while two upper doors slide to each side. As is conventional, the stairwell platform is latched into place in both the retracted and extended position. This arrangement is problematic from a reliability standpoint in that three doors sliding in different directions must match in the closed position. This arrangement is also complicated and expensive to manufacture.
U.S. Pat. No. 3,795,205, provides another example of a sectioned door assembly where the stairwell is made to both retract and form a portion of the outer door. This arrangement is expensive, complicated, and suffers from the same reliability problems discussed above.
U.S. Pat. Nos. 847,501; 995,889; 1,198,357; 1,425,149; 3,913,497; 3,924,545; 3,957,284; and 4,020,920, are all attempts to solve the same problem of providing a reliable passenger door and stair arrangement for high and low platforms. Each of these patents suffer from the same defects discussed above with regard to the other patents. Thus, an improved door design is required. Accordingly, the present invention seeks to take an altogether new approach to creating a reliable door assembly for allowing passenger ingress and egress at both high and low platforms that is reliable, cost effective, and requires relatively little maintenance or adjustment.
Features of one or more aspects of the invention are to increase the reliability of door assemblies in passenger rail cars for use with both high and low platforms.
One or more aspects of the present invention may solve one or more of the above problems and/or provide improved techniques for implementing passenger car door assemblies.
In one aspect of the invention, sectioned door assemblies in existing cars may be retrofitted by fixing the upper door assembly to the lower door assembly in a fixed relationship, thus substantially increasing the overall reliability of the overall door assembly. Where a sectioned door assembly having an integral latch is utilized in one embodiment, another aspect of the invention is to replace the latch such that it no longer is integral with the door.
These and other features of the invention will be apparent upon consideration of the following detailed description of preferred embodiments. For example, using designs in accordance with aspects of the present invention, it is possible to construct a passenger car rail door that is free from binding when the rail car racks and twists. Further, in some embodiments, only a single point of adjustment is required. Although the invention has been defined using the appended claims, these claims are exemplary in that one or more aspects of the invention are intended to include the elements and steps described herein in any combination or subcombination. For example, it is intended that each of the above aspects of the invention may be used individually and/or in combination with one or more other aspects of the invention defined above and/or in connection with the detailed description below. Accordingly, there are any number of alternative combinations for defining the invention, which incorporate one or more elements from the specification, including the description, claims, aspects of the invention, and/or drawings, in various combinations or subcombinations. Accordingly, it will be apparent to those skilled in the art of rail car design, in light of the present specification, that alternate combinations and subcombinations of one or more aspects of the present invention, either alone or in combination with one or more elements and/or steps defined herein, may constitute alternate aspects of the invention. Implementation of the invention in various alternate designs is within the skill in the art and intended to be covered by the appended claims. It is intended that the written description of the invention contained herein cover all such modifications and alterations.